Probing metabolic activity of deep subseafloor life with NanoSIMS

Author(s): Morono, Y.; Terada, T.; Itoh, Motoo; Inagaki, F.
Author Affiliation(s): Primary:
JAMSTEC, Kochi Institute for Core Sample Research, Kochi, Japan
Marine Works Japan, Japan
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: There are very few natural environments where life is absent in the Earth's surface biosphere. However, uninhabitable region is expected to be exist in the deep subsurface biosphere, of which extent and constraining factor(s) have still remained largely unknown. Scientific ocean drilling have revealed that microbial communities in sediments are generally phylogenetically distinct from known species isolated from the Earth's surface biosphere, and hence metabolic functions of the deep subseafloor life remain unknown. In addition, activity of subseafloor microbial cells are thought to be extraordinarily slow, as indicated by limited supply of nutrient and energy substrates. To understand the limits of the Earth's subseafloor biosphere and metabolic functions of microbial populations, detection and quantification of the deeply buried microbial cells in geological habitats are fundamentally important. Using newly developed cell separation techniques as well as an discriminative cell detection system, the current quantification limit of sedimentary microbial cells approaches to 102 cells/cm3. These techniques allow not only to assess very small microbial population close to the subsurface biotic fringe, but also to separate and sort the target cells using flow cytometric cell sorter. Once the deep subseafloor microbial cells are detached from mineral grains and sorted, it opens new windows to subsequent molecular ecological and element/isotopic analyses. With a combined use of nano-scale secondary ion mass-spectrometry (NanoSIMS) and stable isotope-probing techniques, it is possible to detect and measure activity of substrate incorporation into biomass, even for extremely slow metabolic processes such as uncharacterized deep subseafloor life. For example, it was evidenced by NanoSIMS that at least over 80% of microbial cells at ∼200 meters-deep, 460,000-year-old sedimentary habitat are indeed live, which substrate incorporation was found to be low (10-15 gC/cell/day) even under the lab incubation condition. Also microbial activity in ultra-oligotrophic biosphere samples such as the South Pacific Gyre (i.e., IODP Expeditions 329) will be shown. Our results demonstrates metabolic potential of microbes that have been survived for geological timescale in extremely starved condition.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 22 Environmental Geology; East Pacific; Expedition 329; Integrated Ocean Drilling Program; Metabolism; NanoSIMS; Pacific Ocean; South Pacific; Southeast Pacific
Coordinates: S455800 S235100 W1230900 W1660000
Record ID: 2015092571
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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